burrows



June 17 19 24. R 15,859

' c. w. BURROWS umon pr AND APPARATUS FOR 1-:

511m MAGNBTIZABLE OBJECTS a! MAGNETIC" LEAKAGE original Filed on; 4;. 1G1? 3 Sheds-Sheet 1 INVENTOR Clear-Zea WBur-rowa ATTORNEY c. w. BURROWS IBTHOD OF AND APPARATUS POR TESTING IAGNBTIZABLE OBJECTS BY MAGNETIC LEAKAGE June 17 Original Fileq Oct. 4, 1917 s Shts-Sheet 2 A x W\\/1 7 INVEN OR' WBur-rawa CILar L95 ATTORNEY 1 June 17 1 2 I Re. 15,859

' p. w. BURROWS IETHOD OF AND APPARATUS FOR TESTING HAGNETIZABLB OBJECTS BY MAGNETIC LEAKAGE 7 Original Filed Oct. 4. 1917 ;shee'ts-s:-.ez 5

F "1 1' ll- /:9' I

. INVENTOR 2 E CJzar-les WBurrows Reiaued June 17, 1924.

v UNITED .srATEs w. BUBROWS, or sou'rn omen,

ASSIGNMENTS, TO BURBOWB NEW JERSEY, ABSIGNOB, BY DIRECT m MAGNETIC EQUIPMENT CORPORATION, 01

JERSEY CITY, NEW JERSEY, A CORPORATION OF DELAWARE.

men or urn nrr nurus roe. rnsrme menn'rxzanm oneness meumc LEAKAGE.

ori ami Io. means, dated reissue filed Kai-ch 14,

1'0 all whom it may concern: y

Be it known that I, B mnows, a citizen of the United States, and a resident of South Orange, in the'county of 5 Essex and- State of New Jersey, have in-' vented a new and Improved Method of and Apparatus for Testing Ma etizable Objects by Magnetic Leakage, 0 which the following is a full, clear, and exact descri t1on.' 10 This invention is a novel method 0 and apparatus for detecting the resence of inhomogeneities in magnetizab e metal bodies,

. and such as rods, ca les, rails, etc.

The method consists in the determination ll of variation in one or more of the magnetic properties of a'bod of magnetizable material, which variatlon 'may exist between difierent' parts of the specimen examined, and is based upon the principle that there is 20 one and only one set of mechanical characteristics correspondin to a, iven set of magnetic "characteristics, an conversely there is one and only one set of magnetic characteristics corresponding'to a given set at of mechanical characteristics. q

In the practical application of this method each element of length of the specimen is subjected to the action of a magnetic field. This may be accomplished either by causing to the field to, move over the specimen onthe specimen tomove through the field, If the magnetic field be kept constant any variation in ma etic induction will be due to a corresponding variation in material and the 85 change in induction may be measured bymeans of a detectin device comprising one or more test coils w ich move relatively. to"

the specimen. However, to the difiicult ofmaintaining a uniform ma etic 60 fiel I so arrange my detecting device as to be sensitive solely to. leaka e tines insensitive to variations or I uctuationsv in field.

An essential feature of the methodis thiit 45 the tes't'coil is placed within the field and the current in the detectoij is roduced or varied solely by magneticlea in the linesof force in thespecimen being tested, any flaw or. inhomogeneityflin ge .50 the specimen causing a deflection oi lea November 18, 1919, Serial No. 194,756, fled October 4, 1917. Application (or 1924. Serial No. 699,802.

lines of force, and disturbing the lines of force which normally pass through each element of the length of the specimen undergoing inspection if the same 1s perfect.

In other words, in carrying out the method, each element of length of; the specimen to be inspected is subjected to magnetization by a magnetic field, the test coilor coils are placed within this magnetic field adjacent the specimen and relative motion is produced between the magnetic field with the test coil and the specimen, and-so long as the specimen is uniform there is no chan from section tosection of said specimen in the parallel flow of lines of force, but wherever an imperfection, inhomo neity or flaw occurs in the specimen, a Fe akage occurs, which leakage eruption or irruption of lines of force will link through the test coil and. produce a current in such test coil which current me be indicated by a suitable apparatus an may be recorded or announced; thus, the existence-of such flaws can be demonstrated visually, and also i may be recorded if desired, and actually located in the specimen."

Various apparatus may be designed for out the" method aforesaid, and" carrying in he accompanying drawings, .I' have shown apparatus especially designed for testing cables,.rods, rails and other lon -.magnetizable bodies by this method an the invention is hereinafter more fully explained with reference to said drawings to enable others to readily-understand, adapt and use my invention, and the claims sum- -marize the essentials *of the invention and novel featuresof construction andcombina-- tion of parts of, the apparatusffor which protection isdesired. 5 Insaid'dra Fig.1 is a.di

' at w-o a testing pparatus,

Fig. 2 is. aside elevation of 055, practical form of apparatus for carryingofit the invention, i

Fig. 3 is an enlarged part side elevation and part sectional view.through the magnet of the apparatus shown in Fig. 2, Fig. 4 is'a top plan view of 3,

. normal to the axi'sof magnetic flux 'through the fmagnetic field; and then more test coils E, and t Fig. is an enlarged end view and part sectional view showing one of the rotatable m etic poles,

1 1;. 6 is a dia mmatic elevation of a modified form of t e apparatus,

Fig.7 is a sectional elevation of the part of 1g 5, showing the major coil and a detecting coil,

Figs. 8, 9, 10 and 11 are detail views illustrating some of the various possible arrangements of test coils related to the object being tested.

In practically using my invention means are provided for magnetizing the specimen, or successive portions of the specimen to be tested if it be long, like a rod or cable for example, 'and in connection therewith detecting mearfsor test coils are provided located within the magnetic field and preferably closely adjacent the s imen, the detecting means or test coils being kept stationary relatively to the main magnet, or

roducing a relative movement between t e specimen and such test coil either by moving the m etic field and test coil along the specimen ing' tested, or moving the imen through or past the magnetic field and test coil.

To simplify the explanation of the invention and facilitate an understanding thereof, I will first describe a very sim is form of apparatus for testing rods or cab es, and thereafter explain the at present preferred form of apparatus for testing mine cables. I 7

Referring to the diagram, Fig. 1, A re resents a specimen bar, rod, cable or li e object of iron, steel or other ma etizable metal. Preferabl surrounding is specimen'is a solenoid which is connected with a suitable source of electricity, indicated at C, by which the solenoid is energized and caused to producea powerful magnetic field around and in the portion of the specimen A within the solenoid. I. have shown a solenoid in Fig. 1, but any other suitable electro-magnetor magnets might be used, so arranged adjacent the s imen A so as to produce a magnetic fie dtherein. The lines of force of such magnetic field are conventionally indicated by the dotted lines D. Within this magnetic field and ar-,

ranged close to the ob'ect A are one or see test coils may be arranged either parallel with or-at angles to the axis of the specimen, said test coils E are insulated from the solenoid and are connected with a galvanometer or other indicating device G, which should be a sensitive instrument. If a single test coil E is used, it must be positioned with its axis assing imen, so that variations in through cation 1n the magnetizing current Q; coil Bw'll not produce any in them through a magnetic field, suc "produced by the solenoid B for example,

the instrument G. If two or more test coils are used in series, they may be any angle with respect to the axis of the body of magnetic ux, but if the axes of the coils are not normal to the axis of magnetic flux, the coils must'be bucked so that the instrument G will not respond to variations of the magnetizing current, but

'will respond solely to leakage lines of force placed at of the specimen,

the indicating device G produced provided the specimen is uniform throughout; but if in the course of this movement there should be a flaw or other defect in the specimen A, when such flaw enters the magnetic field it causes an eruption or irruption or leakage, of the lines of force in the s imen. For instance, if there should 83 a flaw in the specimen at the point marked a in Fig. 1-, .there will be a leakage of lines of force at such point and when itpasses the test coil E, these leaking lines of force, will aflect the coils E, and produce a change of electromotive force and current therein, and if a vsuitable indicating or recordin device is provided at Gthe presence of suc 1 flaw or inhomogeneity will be detected by reason of such change of electromotive force in the coil and can thus be located in the specimen. If a suitable indicator is provided its pointer will move in one direction as the flaw approaches the test coils E and upon the fundamental fact of observation above statedto wit that there is one, and only one set of mechanical characteristics correspondingto a given set of magnetic characteristics, and conversely there is one, and only one, set of magnetic characteristics corresponding to a given set of mechanical characteristics.

I am aware that it has heretofore'been proposed to test metallic objects by. assing as is the. solenoid being connected in circuit with an indicator orammeter and fiuctuationspf the meter indicat g s me flaw or mcan be detect homogeneities in the object; but such apparatus is inefiicient and unreliable, because only i very lar e inhomogeneities r flaws thereby, and even these cannot be detected with certainty because the efiect or variation in the current through the solenoid B caused by even considerable inhomogeneities in the specimen A rela-- tively is very minute. i

In my invention I do not employ variations in the exterior solenoid or magnetic field producing means for determining defects in the specimen, but instead I use an inde endent or separate detecting means whic is afiected directly and solely by variations in the leakage of ma net'ic lines of force in th specimen, such eakage oc-' curring at any pomt of thespecimen where a flaw or in omo neityv exists, and such leaking lines of gdrce being directly cut by the test coils and producing a relatively violent action of the galvanometer or indicator; and in practice by my method and apparatus I can detect'flaws or inhomogeneities in s cimens which it would be impossible to etect by connecting the solenoid B with an ammeter.

I am aware also that attempts have been made to detect inhomo eneitles by using test coils which are -aected directly by variations in the totality of magnetic lines of force, but these attempts have proved impracticable, because the coils were not so positioned orso coupled as to be insensitive to variations other than those produced by inhomogeneities in the specimen under test. In the arrangement illustrated in Fig. 1, fluctuations of current in the energizing coil B will produce no efiect on the indicating instrument G, because the coils E lie edge-- wise to the normal magnetic flux generated in the specimen A, but when a flaw a is encountered, the 'flux is distorted and lines" of force which are projected out of parallel with the main body of the flux are linked through the coils E and produce an indication in the instrument G. This in-' strument, thererore, is affected solelyb dis- I turbances indicative of inhomogenei les or flaws in the specimen. So insensitive are the test coils, as I arrange them, to variations in the magnetizing current in coil B mgne would result that ;there is no appreciable deflection of the needle in instrument G even when coil. B, is connected to-br disconnected from the source of current C, whereas with apparatus heretofore used, the sudden yariation in flux produced by connecting or disconnecting the coil to the source of current in inducing currents in the test coils of-such strength as would be likely to impair or seriously strain the delicate indicating instrument connectedin series with 1 thetestcoil.

In .commercml p actice, it is Impossible to maintain an absolutely uniform flow of current and with detecting apparatus as heretofore proposed, no provisionhas been made to prevent variations in fiux produced by variations of the magnetizing current from affecting the test coi s. The essentially novel feature of my method of and apparatus for testing magnetizable objects by magnetic leaka e consists in so arranging the test coils that they will be insensitive to any variations of flux except variationsthat result in lines of force that deviate from the direction of travel of themain body The em loyment of such detecting means or test coi s in a ma or so coupled as to e afiected solel by the leakage of lines of force into or rom the specimen. in the manner stated, is'the sentially novel feature of my method and apparatus for carrying out such method.

etic field so positioned he apparatus shown in Figs. 2-5 is par-,

t-icularly designed for testing mine and elevator cables, rods, etc., and I will explain such: apparatus and the manner of using same for testin cables to further elucidate the practical va ue of the invention.

Referring to Figs. 2-5, 1 designates an iron base plate or yoke to the opposite ends of which are securely attached iron cores 1, on-ewhichunay be placed brass spools '1" wound with wire 1, these spools and coi-es forming with the yoke a powerful electromagnet- The terminals of the coils may be suitably connected to binding posts 2 and 2 of any suitable kind attached to the yoke 1, so that the said coils may be readily connected with any suitable source of electricity to ener%ze the same as will be readily understood y those skilled in the art. To the upper end of each core 1' is connected a head 3, which is provided with supports 3 for a rotatable pole-piece 4, which pole-piece has trunnions 4 referably supported by ball or roller bearings 40 in the supports 3 so that the ole-piece can freely rotateon the head 3. e pole-piece extends through cylindric openings in projections 3?, formed integral with the heads 3 and intermediate the supports 3', said projections having openings for the passa of the pole-piece 4 and slightly greater in diameter than the external diametervof the ole-piece which extends therethrough, see ig. 5, 'so indicated at 4', between the pole-piece 4 that there is a slight air gap,

and the surrounding walls of projections 3 and consequently there is no actual frictional or sliding contact between the-pole-plece and the head; and the poleiece while strongly magnetized is not loc ed against rotation.

' The yoke support adgacent the run of the cable C, s3

that the ca lewill lie'in the grooves 4} '1 can be attached to any suitable run vely from one poleiece to the other. Each pole-piece is pre erably provided with a groove 4 intermediate the projections 3' which groove serves to guide the I cable C, or other specimen being tested, and the pole-pieces being strongly magnetized attract and .hold the cable in the ves 4 while permitting the cable to freely move endwise therepast.

When the ct is energized a ma etic field will be established and there will be a flow of lines of force between the lepieces 4 and through that section 0 the" cable lying intermediate the pole-pieces 4,

II which section will be strongg magnetized. and whether the cable be mov through the magnetic l'nld or the along the cable the section of the cable at any time'intermediate the polepieces 4 will a be magnetized in substantially the same manner that the section of the imen A within the solenoid B (Fig. 1) 1S magnetized Intermediate the pole-pieces 4 is arran a detecting means or test coil or coils such testcoils may be variously shaped and located. As shown in Fig. 2 a rectangular coil E is preferably bent to partially surrou'ndthecable()andarrangedtolieclose thereto without actually contacting therewith. However, it is essential coil E be located intermediate between the pole pieces! at a point where the etic flux 1s undisturbed by u nations which might arise from slight variations of contact between the specimen and the pole pieces. TheterminalsofthistestcoilE are connected with an suitable electric indicating or recordi cate electromotive force in the resent magnetic field be moved solenoid are arra according to thenature or evice G, adapted to .indichangfi 0 test coil. 1 e construction'of such indicator ,or-recorderisnot aIfeatm-e ofthe' form to-the pomible to the cross section contour in detected and located. In practice one or more of such testing apparatus could be installed permanently at any suitable point or points in the run of the cable, and tests thereof be made continuously or at frequent intervals, as desired; and when a defect arisesin the cable such defect can be detected'and located in the cable. I

Such a paratus could be used for testing rails, s, or other mafinetizable objects havingconsiderable lengt If such appa ratus should be used for testing nods or rule, the ap aratus could itself be moved along the rai s instead of moving the rail past the ap aratus. so

simple form of apparatus for testing rails or bars is shown in Fi 6 and 7. As shown in these figures a soenoid B is attached to a frame F provided with rollers f at its ends so that the solenoid can be slipped over a bar or rail, indicated at R, and be movably supported thereon by the rollers f. The F may carry an-electric'motor M which is operatively connected by suitable gearing and shafti such as N, N N with one of the rollers and when the motor is running it propel the frame and solenoid, lengthwise of the rail. Within the one or more test coils E which are suita ly electrically connected with an indicator or recorder G. When the current is turned on and the' main magnet energized the apparatus is caused to travel along the rail and any defect or neity intherailwillbe detected inthemanneibn described. 11s 58 e or more test co' may employed contour of h specimen bei tested, andsuchcoilsma be arranged eitlle r with their :ith or at angles, to the longitu axis of the imen being tested; but, such test coils s ould be so arranged adjacentthe that they will intercept or cut lines offorce leaking from such specimen. w 130 Where it is feasible to surround the men with 'a as coil I prefer to have a test with their axes parallel coils arranged the axis the specimen andcloee thereto as in Fig. 8; and in somecases to 118 use a plurality of'test' coils wound'in'series but oppositely as indicated in 8: wherein test coil E' is geferably wound oppositely to test coil If the specimen is regnlar, the' coils might be shaped to conspecimen as indicated in Fig. 9: A plurality of flat coils may be laced around adlacent the withm the magnetic d so as to conform as nearly as ofth' specimentobetediedl Itwillbeevidentthatacoilgcededgeelectrical "mace direction of flutis 'valent offtwo coils -H;

but with their us so that one coil bucks the other coil, for,

in the first case, we have two bucking elements by reason of the fact that electromotive force induced in one half of the coil that lies edgewise to the flux is bucked by electromotive force induced in the other half of the coil. ,However, lines of force the other or wi rounded that leak out of the specimen and hence out of rallel with the direction of the main y of the flux, will pass through the coil and induce electromotive force of opposite potential in opposite sides of the coil, therey inducing a flow of current which is in-- dicated in the instrument G. If the test coils are arranged as in Fig. 8, leakage lines will pass through one ,coil without afiectin pass first through one co and then through the other; hence, inducing currents in these coils which will be indicated on the indicatin instrument.

In some cases, the'coi may bearranged beside the imen with their axes parallel with the axis of the s cimen as indicated in Fi 10, wherein coil E is arranged beside e web of the rail. In such cases, however, two coils E must be employed, one bucking the other so that the coils Wind 10tbe responsive to any fluctuations except those of leakage lines that are intercepted.

The test coils mightin some cases be advanta usly arranged one inside the other as in 11,'where an inner test coil E surroun the object, and is in turn surby an outer test coil E, the said E' and E being oppositely wound and connected in series. In such cases, the normal flux passes through both coils and any variations in this flux will result in induced Y electromotive forces which oppose each other and hence give no reading on the instrument but when leakage lines are inthey will, as the pass out of'the inner coil and through t e outer coil, in-,

. duce electromotive force that will be indimg incated on the instrument.

I do not consider my invention restricted to any particular construction or relative arran ent of test coils, the essential being at a suitable test coil, or detecting means, be located adjacent the specimen being tested and within the magnetic field so that said test coils ordetecti-ng means will be afiected solel by: the leakage of magnetic lines. of orce in, from or to sea specimen.

1. The method of detecting inhomogeneities in magnetizable objects consisting in placing the object in a'magnetic field, plac said magnetic field a testing means insensitive tovariations in the main body of magnetic flux, and observing electrical characteristics induced in said testindg' means by leakage lines of force from sai object.

2. The method of detecting inhomogeneities in magnetizable objects consisting in placing the .object in a magnetic field, placmg in said magnetic field a testing means insensitive to variations in the main body ofmagnetic flux, producing relative movement between said object and said testing 'means and observing the electrical characteristics induced in said testing means by leakage lines of force departing from or entering into said object.

3. The method of directing inhomogeneities in magnetizable objects consisting in placing the object in a magnetic field, placmg in said magnetic field adjacent the body a test coil insensitive to variations in the main body of magnetic flux, and observing variations in electrical characteristics induced in said test coil by leakage of lines.

of force from or into said object.

4. The method of detecting inhomogeneities in magnetizable objects consisting in placing the object in a magnetic field, placing a test coil in said magnetic field adjacent the body, rendering said test. coil insensitive to variations in themain body of magnetic flux, roducing relative movement between said a ject and said testin means,

and observing the characteristics 0 the current induced in said testing meansjby leakage lines of force departing from or entering into said ob'ect.

5.'The metho of ties in magnetizable objects consisting in lacing the object in a magnetic field, Biscing in said magnetic field adjacent the dy a test coil having certain elements thereof bucked against other elements thereof with res ct to electromotive force induced therein y variations of the normal flux of said field, roducing relative movement between, said object and said test coil, and observing characteristics of the current induced testcoil solely -b lines of force leaking-gut of or into said 0 ject.

'6. The method of detecting inhomogeiiei detecting inhomogeneities in magnetizable objects consisting 1n lacingthe object in a magnetic field, placmg cent the object, said conductors being connected in bucked relation with respect to electrical conductors in said field adjaelectromotive force induced thereinb variations in the normal flux of said fie d, producingrclative movement between the ob ject and said conductors, and observ' characteristics of the current induced in sai conductors by leakage of lines of; force from or into said object.

7. The'method of de ecting inhomogeneities in magnetizable o jects, consisting in subjlecting successive sections of suck: body to t e actionof a ma detecting means insensitive to variations in the main' body of magnetic flux, produc ng relative movement between the etic field in I the magnetic field an adjacent the lfiy a detecting surface of th means and the body Within said field, and observing fluctuations of electromotive force induced in the detecting means by the chan e in leakage of lines of force from the body interce ted b said testin means.

' 8. T e me 0d of detecting inhomogeneities in magnetizable specimens consisting in producing a magnetic field, subjecting successive portions of such specimento said field b producing relative movement of said fie d along the length of the specimen, placing within said fie d and adjacent the e specimen a test coil insensitive to variations in the main body of magnetic flux, and observing the variations 1n current from said test coil produced by leakage of magnetic lines of force from or into said specimen during the relative movement of such specimen and test coil.

9. The method of detecting inhomogeneities in magnetizable specimens consisting'in producing-a magnetic field, subjecting successive portions of such specimen to said lines of force from a =fiuctuatmg field b producing relative movement of said field a ong the length of the specimen, placing within said field and adjacent the surface of the specimen a test coil having certain elements thereof bucked against other elements thereof so that no flow of current will be induced in the coil b 4 variations in the main body of magnetic ux, and observing variations in the-electromotive force from said test coil produced solely b variations in. the l of magnetlc es of force from or into said specimen during the relative movement of said specimen and 10. The method of detecting leakage .of

lines of force from a fluctuating magnetic a test coil field which consists in placing in the field with .the axis of the coil normal to the main body of magnetic fiux, and observing the electrical characteristics of the current induced in the coil lines which deviate from the main body 0 flux and link thro the coil.

11. method of detecting leakage of magnetic field which consists in plae' coils in the field, one coil, ing bucked mthe other, and obse electrical ristics' of the current the test coils as they are w y cut by linesofforcethatdeviatefromthemain bodyof ic flux.

12. Apparatus fol-detecting mhornogeneitiesinmagnetizable netlzmg' lbOd n; 'neticfield adj zcentthe Edy, said detec t in g means comprising conductors connected in bucked relation with respect to electrometive force induced therein by variations in the normal flux of said field, and means for electrical v =1 of cur.

two coaxial the cable, detecting means objects, means for magrent produced in the detecting means by leakage of lines of force from said body.

13. Apparatus for detecting inhomogeneities in magnetizable objects, means for producing a magnetic field around an object, a test coil with its axis perpendicular to the normal flux of the ma etic field, and means for indicating the e ectrical characteristics of current induced in said coil by leakage of lines of force fromsaid object.

14. Apparatus for detecting inhom neities in magnetizable ob'ects, means or producing a magnetic fiel around an obect, a 'detectin circuit comprising two elements connecte in electrical y opposed relation with respect to variations in the normal flux of the magnetic field, and means for indicating electrical characteristics of current induced in said coil by leakage of lines of force from said object.

15..Apparatus for detecting inhomo neities m-magnetizable objects, means or producing a magnetic field around said obect, two coils surrounding the obtjzct, said coils being connected in series but ing oppositel wound, means for producing movement between said object and detect means, and means for indicating electrica characteristics of current induced in said coils by leakage of lines of force from said 'a f a ma 16. paratus, or etec om neities etizable obje t z tg comp '08:. means for pr ucing amagnetic field aroun the specimen to be tested, a test coil said magnetic field adjacent the specimen, said test coil comprising elements that are bucked with respect to electromotive force '1' of the like, means for the cabls, means for producing resultant magnetic field longitu V of in said 31%.- cent the cable, said being insensitive to variations of magnetic flux the cable and means .for indi vanations of the electromotive vforce need in said detect" oflinssof foil-(gs gom i inhtp'the cable. dad magnet vmg' a-core rovi wi a head, a pole piece rotatably mounted on said head and spaced therefrom, and roller supporting said piece on the 19. A magnet forspecifid,

lll'

comprising a. metallic base, cores attached thereto, coils surrounding said cores, heads thereto, coils surrounding said cores, rotatattached to said cores, rotatable 1e pieces able pole pieces mounted on and spaced from mounted on and spaced from the ea'ds, and 10 the cores, and roller bearings supporting the roller bearings supporting the pole pieces I pole pieces on the cores. on the heads;

20. A magnet for the purpose specified comprising a metallic base, cores attached CHARLES W. BURROWS. 

